Polymerization in the presence of dibutyl sulfite as an accelerator



Patented Feb. 27, 1951 POLYMERIZATION IN THE PRESENCE OF DIBUTYL SULFITE AS AN ACCELERATOR John a Loritsch, Scotia, N. Y., assignor to Gen- 1 eral Electric Company, a corporation of New York No Drawing. Original application July 23, 1946,

Serial No. 685,773. Divided and this application November 24, 1948, Serial No. 81,930

2 Claims. (Cl. 2611-45-4 This application is a division of my earlier filed application, Serial No. 685,773, filed July 23, 1946, and assigned to the same assignee as the present invention.

This invention relates to the polymerization of compounds containing polymerizable groupings. More particularly, this invention is concerned with'a method of accelerating the rate of polymerization of a substantially non-aqueous polymerizable system containing an organic oxygenreleasing peroxide catalyst and a polymerizable com-pound capable of being polymerized by the aforementioned organic catalyst, e. g., a polymerizable compound grouping or a -CH=CH grouping which method comprises incorporating in the said system a small amount of an organic're'ducing agent capable of being oxidized by the addition of an atom of oxygen released from the said organic catalyst, and thereafter'efiecting polymerization of the resulting mass.

In the polymerization of chemical compounds or compositions containing polymerizable groups or radicals of the type disclosed above (for brevity referred to hereinafter as the polymerizable compounds), it is often desired to accelerate the conversion of the monomeric material or, in some cases, a substantially unpolymerized material to the Polymeric form or substantially polymerized state. For this purpose, catalysts are incorporated in the polymerizable mixture. However, despite the use, in some cases, of quite active catalysts, e. g.,, benzoyl peroxide, aluminum chloride, etc., it is often difficult to effect the accelerated polymerization without obtaining products having certain defects.

For instance, when benzoyl peroxide is employed as a catalyst for the polymerization of a polymerizable system containing an unsaturated aliphatic alcohol ester of a polycarboxylic acid, e. g., diallyl phthalate, and a polyhydric alcohol ester of an alpha unsaturated alpha, beta polycarboxylic acid (said polyhydric alcohol ester being often referred to as an unsaturated alkyd resin), e. g., diethylene glycol maleate, great care must be exercised in effecting the polymerization. If too large an amount of benzoyl peroxide is employed, the type of copolymer obtained will be inferior due to the low molecular weight of the roduct. If a small amount of benzoyl peroxide is employed, the time for eflecting reaction is greatly extended. In addition, if the time containing a CH2==C for eflecting polymerization is attempted to be decreased by heating the polymerizable mass at higher temperatures, quite often the polymerized product will contain bubbles, cracks, voids, etc.

I have now discovered that polymerizable sys-- terns of the kind mentioned in the first paragraph of this specification, more particularly such systerns comprising polymerizable material containing a CHz--C radical or a plurality of such radicals, or polymerizable material (other than, e. g., drying and semi-drying oils and acids thereof) containing a CH=CH radical or plurality of such radicals, may be polymerized at a much faster rate than has heretofore been possible to produce polymerized products having an appearance and properties comparable to products po ymerized for much longer periods of time in accordance with the better techniques now employed in the art.

In accordance with the practice of the more specific embodiments of my invention, I am able to effect more rapid conversion of the abovedescribed polymerizable materials or compositions of matter to the finally polymerized state by incorporating in the polymerizable material (e. g., the polymerizable compound or compounds) a small amount of an organic oxygen-releasing peroxide catalyst, adding to the polymerizable system a small amount of an organic reducing compound as illustrated, e. g., by the following groups oi compounds: (1) organic reducing compounds corresponding to the general formula where R is selected from the class of substitu ents consisting of organic hydrocarbon radicals,

for instance, alkyl, aryl, alkaryl, aralkyl radicals, alkoxy, and aryloxy radicals, and R is the same as R and in addition may be a substituent selected from the class consisting of hydrogen and hydroxy substituents; a more specific example of such class being organic compounds containing phosphorus and an oxygen atom attached directly to the phosphorus atom, e. g., organophos-phorus compounds having the general formula where R is an organic radical, e. g., a hydrocarbon radical, more particularly one selected from the class consisting of alkyl, aryl, alkaryl, and aralkyl radicals, and R isa substituent selected from the class consisting of hydrogen and organic radicals which may be the same as R (supra); (2) organic reducing compounds containing sulfur and'an oxygen attached directly to the sulfur, e. g., organosulfur compounds having the general formula where R. and B have the same meaning as disclosed above. One of the requirements for the above-disclosed organophosphorus and creamsulfur compounds is that these compounds contain a phosphorus or sulfur atom the valence of which can be increased by the addition of an atom of oxygen released from the peroxide catalyst.

Inpracticing the present inventiomit is essential that certain precautions be taken in the type of organic peroxide or type of organic reducing compound employed. For example, certain organic peroxide catalysts, for instance, benzoyl peroxide, exert no additional accelerating effect on the polymerization of'the generically described polymerizable compounds (or compositions) when used in conjunction with 'the organic reducing agent of the type disclosed above when compared with the case where the organic reducing agent is absent. The reason for this is not clearly understood. However, one explanation for this 4 In the presence of the usual types of inhibitors, e. g., hydroquinone, the dissociation proceeds according to (a) and (b) of the above equation. This reaction is shown by the following equation:

However, when teritary butyl hydroperoxide is used with, the type of reducing agent employed in the practice of my invention, the reaction of this type of reducing agent, e. g., phenyl phosphinic acid, whose formula may be written as may depend upon the manner in which benzoyl peroxide dissociates.

Benzoyl peroxide, for example, dissociates in the presence of a reducing agent of the type disclosed above according to-the following equation:

0 arm-4L0.

type employed in the practice of my invention are caused to dissociate, the reaction is believed to proceed as illustrated, e. g., by tertiary butyl hydroperoxide:

cim-o. .011

(hue-OH H20 with tertiary butyl hydroperoxide proceeds according to (c) of Equation 2. Expressed by means of an equation, the reaction would appear as follows:

The free radicals when thus released in a reactive ,medium arebelieved to initiate polymerization which causes the polymerization to proceed at an accelerated rate.

Generally, in accordance with the practice of my invention, it is believed that all reducing agents which reduce by acquiring an atom of oxygen promote the acceleration effect. Those reducing agents which reduce by furnishing pr0- tons to another molecule, do not promote accel eration, but rather promote retardation of the polymerization. Stated alternatively, the acceleration eifect is brought about by free radicals released by the reaction between the proper peroxide catalyst and the proper accelerator, the type of accelerator and peroxide used determining the effect produced.

My invention may be applied to the polymerization of various polymerizable monomers and mixtures of monomers. These. include, e. g., the various polymerizable materials or monomers containing the CH2=C grouping, for instance,

styrene, substituted styrenes, e. g., dichlorostyrene, divinyl benzene, vinyl ethylbenzene, etc.; acrylic and methacrylic acids and derivatives thereof including the nitriles of the said acids, e. g., acrylonitrile, the amides of the said acids, e. g.,

acrylamide, esters of an acrylic acid of the general formulawhere R may be hydrogen and, in addition, may be a halogen or a hydrocarbon radical, more particularly one selected from the class consisting of alkyl, aryl, alkaryl, and araikyl radicals, and R auaese i acetate, allyl acetate, diallyl succinate, etc.; vinyl ethers and esters, e. g., divinyl ether, vinyl esters of saturated and unsaturated aliphatic monocarboxylic and polycarboxylic acids, e. g., vinyl acetate, vinyl propionate, vinyl butyrate," divinyl oxalate, vinyl acrylate, vinyl crotonate,--'etc.; vinyl ketones, e. g., divinyl ketone, vinyl ethyl ketone, etc.; saturated and unsaturated monohydric and polyhydric alcohol esters of unsaturated polycarboxylic acids of the itaconic acid type, c. g., diethyl itaconate, diallyi itaconate, ethylene glycol ita-' conate, diethylene glycol itaconate, gly'ceryl itaconate. methyl citraconate, dimethallyl citracohate, diethyl mesaconate, diallyl mesaconate, etc.; vinyl halide compounds, e. g., vinyl chloride, vinyl bromide, etc.; diolefin compounda e; g butadime-1,3, 2-methyl butadiene-ld chloroprene, 2-cyanobutadiene-L3, etc.

Among the compounds containing a grouping which may be poiymeriaed in acoordance with the concept of my inventioh, are, e. g., saturated and unsaturated, monohydj and polyhydric alcohol esters of alpha unsaturated alpha, beta polycarboxylic acids, for instance, diethyl iumarate, 'diethyl maleate, dibgtyl iumarate, ethylene glycol maleate, ethylene glycol inmarate, propylene glycol maleate, dietl'gylene glycol maleate, propylene glycol iumarate, gglyceryl maleate, diallyl maleate, diallyl funiariite, dimethallyl maleate, etc. It will loc -understood by those skilled in the art, that mixtum of compounds containing CH2=C grouping and the CH=CH-- grouping may also be employed as the polymerizable materials Various suitable reducing agents may be employed which in the presence oi the proper organic peroxide catalyst accelerate the polymerization of the above-described polymerizable compounds. -'I'hese include, e. g organic compounds containing a phosphorus. atom to which an oxygen atom is attached directly to the phosphorus atom. the valence oi which can be increased by the addition of an oxygen atom released irom the organic oxygeh-releasing peroxide catalyst, for instance, a l phosphinic acids, e. g., butyl phosphinic id, etc.; aryl phosphinic acids. e. g., phenyl phosphinic acid; dialkyl hydroxy phosphines, e. g diethyl hydroxy phosphine; diaryl hydroxy phosphines, e. a, diphenyl hydroxy phosphine, etc.; alkyl aryl phos phinates, e. g., dibutyl phenyl phosphinate; aryl allryl phosphinates, e. g., diphenjyl butyl phosphinate, etc.; diaryl aryl phosphinates, e. 5., diphenyl phenyl phosphinate, etc.; 'alkyl and aryl phosphites, e. g., phenyl phosphit'e, etc.; organic reducing compounds containing asulfur atom to which an oxygen atom is attacheddirectlyto the sulfur atom, the valence of which can be increased by theaddition oi an oxygen atom released !rom the organic oxygen-releasing peroxide catalyst, e. g., alkyl and aryl sulfltes, for instance, alkyl sulfltes, e. g., ethyl sulfite, n-butyl suliite, aryl sulfites, e. g., phenyl sulflte, etc. The foregoing compounds are only illustrations of the broad class of compounds which can be employed as accelerators within the broad scope of my claimed invention. It is, of course, understood, that mixtures of the above-mentioned reducind agents (accelerators) may also be employed.

The amount of reducing agent employed may be varied depending on such factors as, e. g., the type oi polymerizable materials employed, reac-. tion products desired, temperature conditions, etc. Usually the amount, by weight, may be varied from about 0.01 to 10 per cent of the weight of the polymerizable materills. I prefer to employ from about 0.1 to a or 5 per cent, since no particular advantage is obtained by using; amounts substantially in excess of these amounts. As was stated previously not all organic per oxides are suitable for use in the practice of my invention. Only those organic peroxides which can be induced to give up an atom oi oxygen in the presence of the organic reducing agent, many examples of which have been given above, may be used. These include dialkyl peroxides, alml .hydroperoxides, alkyl esters oi peracids, and

mixed aliphatic and aromatic peroxides all oi which give up an atom oi oxygen in the pmence of the organosuliur reducing agent described above, e. g., acetyl benzoyl peroxide, isopropyl tertiary butyl peroxide, tertiary butyl hydroper oxide, diheptanol, tertiary butyl perberima'te; ditertiary butyldiperphthalate, tertiary butyl per.- iuroate, ditertiary butyl diperadipate, ditertia'ry, butyl dipersuccinate, l-hydroxy cyclohexyi hys droperoxide-l, tertiary amyl hydroperoxide, (iiacetyl peroxide, etc, as well as other suitable all phatic (c. g., alkyl), aromatic or mixed aliphatic and aromatic (e. g., mixed alkyl aryl) peroxides, peracids, hydroperoxides, peracid esters, etc. The amount of organic oxygen-releasing peroxide catalyst employed may also be varied over a wide range depending, for example, on the poly;- merizable materials employed, products desired, temperature conditions, etc. Usually I may employ from about 0.1 to as high as 8 or 10 per cent by weight of the polymerizable materials. I prefer to employ an amount oi the organic peroxide catalyst equal to from 0.25 to about 5 per cent, by weight, of the polymerizable materials.

In order that those skilled in the art may better understand how the present invention may be practiced, the following examples are given by way of illustration and not by way of limitation. All parts are by weight.

Example 1 to stand at room temperature until it was determined that the mixture had gelled. The time required to arrive at this gel stage was taken as the Average time to gel at roomtempera- 5 ture." All parts are by weight.

Ave Dlethyl- Phony] Sample Dlallyl ene mm Phoc- 3$ No. Phthalate Glycol phinio Room Maleate Acid Temp Parts Part0 Part: Helm 1.- 67 33 Benmyl peroxide. 1 part None 1 2 67 33 do 3. 67 33 Diheptancl peroxide, 1 part None About 340 L 67 33 do 1 5. a Tertiary butyl perbenzoate, 1.5 parts Ne ng 62 n o 558 g Dite-tiary Butyl Dlperphthalate, 1.5 parts Nlinfl 5:

n g Tert'ary ButylPeriuroate. 1.5 parts..----- Ni'ing 7:

r n 28 g Dltertlary Butyl Dlperadlpate, 1.5 parts Nc ng 5g 0 c g :3 Dite rtiary Butyl Dipersuecinate, 1.5 parts..----.---- None a; fl 67 3g i-hygroxy eyclohexyl hydroperoxlde-l, 1 part None 3912) 67 n 67 33 Tertiary amyl hydroperoxide, 1 part None 320 67 33 do 12 50 50 Diacetyl, 1.5 parts N one 50 50 do 3 50 50 Away! benzoyl peroxide, 1.5 parts" None 20 50 50 n 6 50 50 Dltertiary butyl peroxide, 1.5 parts. None 90 50 50 do 1. 94 50 50 N n None 96 50 50 N one 2 Greater than 1080 Example 2 for 15 hours at 110 C. In every sample except This example illustrates the results obtained by polymerizing a mixture of polymerizable materials comprising diallyl phthalate and diethylene glycol maleate in the presence of tertiary butyl hydroperoxide and using various reducing agents, including reducing agents which are known to be inhibitors per se for the polymerization of the aforementioned polymerizable materials.

the one in which phenyl phosphinic acid was absent, gelling occurred after the 20 hours at room temperature. The Remarks" in the following table are concerned only with the appearance of the castings after heating at the elevated temperature (110 C.).

gelling properties at the end of 20 hours at room temperature. Thereafter each sample was heated 75 p Ti$Z% %e1 fl 515115 1 agm Parts Catalyst Accelerator at 1m n; t al to em Maleate gg 67 33 N n 340. 50 N 216. 50 50 N 144. 50 50 Tertiary Butyl catechol, 2 parts. Greater than 50 to 0115mm], 2 parts 150. 50 Quinone. 2 p Do. 67 33 Phenyl phosphinlc acid, 2 parts..- 12. 67 33 n-Butyl sulflte, 2 parts 12. 67 33 Diphenyl hydroxy phosphine, 2 60.

8 50 50 Dfiilitenyl phenyl phosphinate, 1 5.

p v 100 Benzoyl Peroxide 6.. None 67. 100 100 do n-Butyl sulilte, 3 part 72.

Example 3 1 Parts Db Parts Parts This example illustrates the advantage which Sam- Parts ethylene Tertiary Phony] can be taken of being able to polymerize matef, ggggg G1 col 3; 1%;? 3 Ma cute p c rials, e. g., a mixture of diallyl phthalate and di- 05 Peroxlde A01! ethylene glycol maleate, at a faster rate and still I 4 T obtain products which have better properties 1 .66 2 Mm vggggdmuy than those of products obtained by eflecting 2 134 66 2 2 very at-g" polymerization of the same materials in omit- 134 66 2 3 very h rdl 'w the accelerating system embodied in my in-' 134- so 2 3.5 vfifi hwffim vention. In each case the polymerizable mate- 134 x 66 2 5 grials were placed in a. glass tube and examined for 134 5 2 6 Do.

[This le showed no signs of gelling alter 20 hours at room tempereturewh c all the other samples were already gelled at that time.

Example 4 of my claimed invention, it is now economically feasible to employ the gelled materials for molding compositions by grinding the gelled particles and molding the same under heat and pressure.

Even though solventless mixtures of the polymerizable materials may be employed for coating or other purposes specified previously, solution of Sample Time To Gel At Room Polymerizable Composition Peroxide Catalyst Accelerator Temp, In Hours 1 Styrene, 40 parts; Propylene glycol, Tertiary butyl hydro- None l4.

fumarate-carbate, 60 parts. peroxide, 2 parts. 2 Same as 1 Same as l Phengl Phosphinic 0.5.

aci 2 parts. 3 Butyl methacrylate, 33 parts; Cas- Same as l.. None 45.

tor oil vinalkyd,; 67 parts. Same as 3 Same as 1 Same as 2 2. Diallyl phthalate, 100 parts.... Tertiary butyl perben- None 8.35 minutes.

zoate, 2 parts. Same as 5 Same as 5 Same as 2 5.4 minutes.'

Methyl metbacrylate, 100 Tertiaryabutyl perben- 0 96.

zoa e, Same as 7 Same as 7 Phen l Phosphinic 24.

aci 3 parts. Methyl methacrylate, 100 parts --do n-buttyl sulflte, 3 18.

par s. Styrene, 33.4 parts; Diethylene do 0 96.

glycol maleate, 66.6 parts. Same as 10. --.do Same as 9 18. Vinyl acetate, 100 parts.. do 0 Greater than 330 hours. Same as 2 do Same as 8 Greater than 330 hr. However, the viscosity was about times that of sample 12 after 330 hours.

' '1 e gelling times in these two cases were determined at 132.2 C.

It will be understood by those skilled in the art that the invention is not intended to be limited to include the specific polymerizable materials, or organic peroxide catalysts, or accelerators. i. e., reducing agents, employed in the foregoing examples. Other polymerizable materials, organic peroxide catalysts, and accelerators as mentioned previously (supra) may also be employed in place of the ones used in the foregoing examples. It will be apparent, also, that the benefits derived at the temperatures employed in the foregoing examples are obtainable, though more pronounced, at higher temperatures, e. g., at 80 to 150 C.

By means of my invention, it is possible to polymerize the aforementioned polymerizable materials in situ in shorter periods of time than has heretofore been possible, while at the same time the possibility of the development of voids, cracks, etc.. in the polymerized piece is minimized. This is especially useful in the case of castings and moldings of such materials which are used, c. g., as dielectrics for capacitors, as bushings, in potting and sealing applications. or for other electrical insulation purposes.

Advantage may also be taken of the accelerated rate of polymerization in other manufacturing procedures. For example, I may use the liquid form of the polymerizable materials containing one of the above-described oxygen-releasing peroxides and accelerators for coating compositions, or as cohesive ingredients in laminates. Since many of the polymerizable compositions are liquids and require no solvent, these compositions can be employed for coating or impregnating applications wherein it is possible to polymerize quite readily the entire impregnating or coating composition without the use of solvents.

In addition, because of the ability to gel the polymerizable compositions so readily by means glycol, 1 mol iumaric acid, and 2 mols carbic anhydride. between 81 parts eastor oil and 17.2 parts maleic anhydride. After cooking to an is eflected by the addition of 1.8 parts pyridine and further heating. (See the polymerizable mass in suitable solvents may also be effected to yield mixtures having decreased viscosities suitable, e. g., for deposition on objects in thin films. Such solutions may be used for wire coatings and other types of insulation including heat and electrical insulation, as acid and alkali-resistant impregnants, etc.

It will, of course, be understood that the polymerizable compositions disclosed and claimed in this invention may be modified further by including fillers, opacifiers, pigments, etc.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. The method of polymerizing a non-aqueous polymerizable system free of unsaturated oils and drying oil acids and containing diallyl phthalate and diethylene glycol maleate, which method comprises carrying out the polymerization in the presence of (a) tertiary butyl hydroperoxide and (b) n-butyl sulfite.

2. A composition free of water and unsaturated drying oils and drying oil acids, said composition comprising the product of reaction of a mixture of ingredients comprising (1) a mixture of diallyl 'phthalate and diethylene glycol maleate, (2)

tertiary butyl hydroperoxide, and (3) from 0.01

to 5 per cent, by weight, based on the weight of (l) of n-butyl sulflte. 1

JOHN A. LORITSCH.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 0 2,382,812 Parker Aug. 14, 1945 2,462,354 Brubaker et al Feb. 22, 1949 2,515,686 Barnes et al July 18, 1950 

1. THE METHOD OF POLYMERIZING A NON-AQUEOUS POLYMERIZABLE SYSTEM FREE OF UNSATURATED OILS AND DRYING OIL ACIDS AND CONTAINING DIALLYL PHTHALATE AND DIETHYLENE GLYCOL MALEATE, WHICH METHOD COMPRISES CARRYING OUT THE POLYMERIZATION IN THE PRESENCE OF (A) TERTIARY BUTYL HYDROPEROXIDE AND (B) N-BUTYL SULFITE. 